be achieved without receiving any credits for  IAQ。

To manage this issue and promote IAQ, some schemes intro- duced mandatory requirements for addressing IAQ。 For example, in the 2009 version of LEED, buildings awarded certification had to meet the requirements of ASHRAE 62。1 ventilation standard [6] and apply the environmental tobacco smoke (ETS) control。 In DGNB, each category needs to receive a minimum number of credits; otherwise, the building cannot be awarded certification。 Although seemingly effective in promoting credits from all categories, DGNB does not mandate which criteria should be addressed within each category。 This approach, as a result, may not sufficiently promote IAQ if credits for other IEQ criteria would suffice and be easier to receive。 Mandating criteria addressing IAQ is further tackled in the Green Mark Pilot 2015 proposed by Building Construction Author- ity in Singapore [10]。 They defined prerequisite requirements for all categories for a building to be awarded certification。 In the case of IAQ, these prerequisites include airtightness and leakage, minimum ventilation rate, filtration media and time of pollution, and the use of low volatile organic compound (VOC)  paints。

In conclusion, credits for IAQ are included in the certification schemes, and some schemes include minimum requirements for IAQ。 It can be argued whether current credits are sufficient and effective to promote better IAQ in green buildings。 Certification schemes mainly require ventilation as the major measure to control IAQ and less so the source control。 A building can receive the highest level of certification, in many schemes, without any credits for IAQ。 Consequently, the fact that criteria addressing IAQ are included in the certification schemes does not guarantee that they are addressed during the certification process。

1。4。 Do green buildings have better IAQ than conventional buildings?

At least three scores of studies have documented indoor envi- ronmental quality in the cross-section of green buildings certified with different schemes, mainly LEED, Green Star and BREEAM [23]。 Some studies compared IEQ in green buildings with matched or unmatched regular (conventional) buildings that were not certified by any green building scheme。 IAQ was examined in about half of these studies [3,23]。

IAQ in green buildings was mainly assessed using post- occupancy surveys, which typically were not the same in various studies。 These surveys collected information on IAQ as perceived by the occupants。 Only in a few studies, the actual measurements of IAQ were carried out by documenting the levels of CO2 or other pollutants, and measuring the ventilation rates, so the actual ex- posures and their levels in the buildings could be described (e。g。, [57,62]。

In general, the studies indicated that the occupants of green buildings rated IAQ to be high or that they were more satisfied with IAQ than the occupants in conventional buildings (e。g。, [1,2,15,21,41e43,54e57,62,79]。 In a few cases, the opposite result was seen; that is, the ratings of IAQ were lower in green buildings compared with conventional buildings [16,53,80]。 In some studies, there was no observed effect of green certification on the ratings of IAQ as reported by the occupants of green buildings (e。g。, [4,52]), or the results of subjective evaluations were equivocal (e。g。, [40])。

A few studies suggested that IAQ was improved in green buildings because of lower prevalence of health symptoms as re- ported by occupants; some of these symptoms can be attributed to exposures to air pollutants (e。g。, [14,21,37,57,62])。 One study, which compared green and conventional hospitals, showed reductions in mortality rates, blood stream infection rates and medicine con- sumption in the green hospital; some of these effects could occur because of improved IAQ [81]。